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Rac-GTPases Regulate Microtubule Stability and Axon Growth of Cortical GABAergic Interneurons.

Tivodar S, Kalemaki K, Kounoupa Z, Vidaki M, Theodorakis K, Denaxa M, Kessaris N, de Curtis I, Pachnis V, Karagogeos D - Cereb. Cortex (2014)

Bottom Line: We show that in the absence of both Rac proteins, the embryonic migration of medial ganglionic eminence-derived interneurons is further impaired.In addition, Rac1/Rac3-deficient interneurons show gross cytoskeletal defects in vitro, with the length of their leading processes significantly reduced and a clear multipolar morphology.We propose that in the absence of Rac1/Rac3, cortical interneurons fail to migrate tangentially towards the pallium due to defects in actin and microtubule cytoskeletal dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece.

No MeSH data available.


Related in: MedlinePlus

MGE-derived interneurons fail to migrate towards the neocortex in double Rac1/Rac3 mutant embryos. Coronal sections from the forebrain of control and double-mutant embryos at E14.5 (A–C′) and E16.5 (D–F′), were stained for YFP and specific markers of interneurons to visualize the migration of MGE-derived cells to the developing neocortex. In the double mutants at both ages (A′–C′, D′–F′: Rac1fl/fl;Rac3−/−;Nkx2.1+/Cre, dmut) Rac1/Rac3-deficient interneurons fail to migrate towards the developing neocortex, compared with the control ones (A–C, D–F: Rac1+/fl;Rac3+/−;Nkx2.1+/Cre, dhet). At E16.5 some of the Rac1/Rac3-deficient cells migrate towards the cortex although the majority remain aggregated in the ventral telencephalon (asterisk in D′–F′) compared with control ones as revealed by immunostaining for YFP and interneuronal markers (Lhx6, E, E′; Sst, F, F′). The number of Lhx6 and Sst-expressing interneurons is severely reduced in the cortex of dmut embryos (B′, C′, E′, F′) compared with control ones (B, C, E, F) at both embryonic stages. Arrowheads indicate the two migratory streams in the MZ and the IZ/SVZ. Scale bars: 100 μm.
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BHU037F1: MGE-derived interneurons fail to migrate towards the neocortex in double Rac1/Rac3 mutant embryos. Coronal sections from the forebrain of control and double-mutant embryos at E14.5 (A–C′) and E16.5 (D–F′), were stained for YFP and specific markers of interneurons to visualize the migration of MGE-derived cells to the developing neocortex. In the double mutants at both ages (A′–C′, D′–F′: Rac1fl/fl;Rac3−/−;Nkx2.1+/Cre, dmut) Rac1/Rac3-deficient interneurons fail to migrate towards the developing neocortex, compared with the control ones (A–C, D–F: Rac1+/fl;Rac3+/−;Nkx2.1+/Cre, dhet). At E16.5 some of the Rac1/Rac3-deficient cells migrate towards the cortex although the majority remain aggregated in the ventral telencephalon (asterisk in D′–F′) compared with control ones as revealed by immunostaining for YFP and interneuronal markers (Lhx6, E, E′; Sst, F, F′). The number of Lhx6 and Sst-expressing interneurons is severely reduced in the cortex of dmut embryos (B′, C′, E′, F′) compared with control ones (B, C, E, F) at both embryonic stages. Arrowheads indicate the two migratory streams in the MZ and the IZ/SVZ. Scale bars: 100 μm.

Mentions: Using immunofluorescence on E14.5 forebrain cryosections from control (dhet) embryos we observed YFP+ interneurons migrating tangentially forming the characteristic two cellular streams in the marginal zone (MZ) and the intermediate/subventricular zone (IZ/SVZ) and entering the dorsal telencephalon ([Tanaka and Nakajima 2012; Marin 2013]; Figure 1A, arrowheads indicate the MZ and IZ/SVZ). These two cellular streams of migrating interneurons were completely absent in the double-mutant embryos (Fig. 1A′). Upon comparison of the YFP-stained sections from the double mutant with equivalent sections from the conditional Rac1 mutant (Fig. 1 of (Vidaki et al. 2012) and data not shown) at subsequent stages, we observed that the double-mutant cells entered the dorsal telencephalon ∼1 day later (E14.5, Fig. 1A′) than the single Rac1 mutant YFP+ cells (Fig. 1 of Vidaki et al. 2012). Analysis with a postmitotic marker of MGE-derived GABAergic interneurons, Lhx6, and a subtype specific marker, Sst verified the severely reduced number of migrating interneurons at E14.5 in the dorsal telencephalon of the double mutants (Fig. 1B,B′;C,C′). Later in embryogenesis (E16.5), in the double mutants, only a few YFP+, Lhx6+, or Sst+ cells were found inside the cortex but not extending as dorsally as in the control mice (Fig. 1D,E,F,D′,E′,F′). In addition, a significant accumulation of these cells was observed in the ventral telencephalon of double-mutant embryos and not in the control ones (asterisk in Fig. 1D′,E′,F′).Figure 1.


Rac-GTPases Regulate Microtubule Stability and Axon Growth of Cortical GABAergic Interneurons.

Tivodar S, Kalemaki K, Kounoupa Z, Vidaki M, Theodorakis K, Denaxa M, Kessaris N, de Curtis I, Pachnis V, Karagogeos D - Cereb. Cortex (2014)

MGE-derived interneurons fail to migrate towards the neocortex in double Rac1/Rac3 mutant embryos. Coronal sections from the forebrain of control and double-mutant embryos at E14.5 (A–C′) and E16.5 (D–F′), were stained for YFP and specific markers of interneurons to visualize the migration of MGE-derived cells to the developing neocortex. In the double mutants at both ages (A′–C′, D′–F′: Rac1fl/fl;Rac3−/−;Nkx2.1+/Cre, dmut) Rac1/Rac3-deficient interneurons fail to migrate towards the developing neocortex, compared with the control ones (A–C, D–F: Rac1+/fl;Rac3+/−;Nkx2.1+/Cre, dhet). At E16.5 some of the Rac1/Rac3-deficient cells migrate towards the cortex although the majority remain aggregated in the ventral telencephalon (asterisk in D′–F′) compared with control ones as revealed by immunostaining for YFP and interneuronal markers (Lhx6, E, E′; Sst, F, F′). The number of Lhx6 and Sst-expressing interneurons is severely reduced in the cortex of dmut embryos (B′, C′, E′, F′) compared with control ones (B, C, E, F) at both embryonic stages. Arrowheads indicate the two migratory streams in the MZ and the IZ/SVZ. Scale bars: 100 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4537417&req=5

BHU037F1: MGE-derived interneurons fail to migrate towards the neocortex in double Rac1/Rac3 mutant embryos. Coronal sections from the forebrain of control and double-mutant embryos at E14.5 (A–C′) and E16.5 (D–F′), were stained for YFP and specific markers of interneurons to visualize the migration of MGE-derived cells to the developing neocortex. In the double mutants at both ages (A′–C′, D′–F′: Rac1fl/fl;Rac3−/−;Nkx2.1+/Cre, dmut) Rac1/Rac3-deficient interneurons fail to migrate towards the developing neocortex, compared with the control ones (A–C, D–F: Rac1+/fl;Rac3+/−;Nkx2.1+/Cre, dhet). At E16.5 some of the Rac1/Rac3-deficient cells migrate towards the cortex although the majority remain aggregated in the ventral telencephalon (asterisk in D′–F′) compared with control ones as revealed by immunostaining for YFP and interneuronal markers (Lhx6, E, E′; Sst, F, F′). The number of Lhx6 and Sst-expressing interneurons is severely reduced in the cortex of dmut embryos (B′, C′, E′, F′) compared with control ones (B, C, E, F) at both embryonic stages. Arrowheads indicate the two migratory streams in the MZ and the IZ/SVZ. Scale bars: 100 μm.
Mentions: Using immunofluorescence on E14.5 forebrain cryosections from control (dhet) embryos we observed YFP+ interneurons migrating tangentially forming the characteristic two cellular streams in the marginal zone (MZ) and the intermediate/subventricular zone (IZ/SVZ) and entering the dorsal telencephalon ([Tanaka and Nakajima 2012; Marin 2013]; Figure 1A, arrowheads indicate the MZ and IZ/SVZ). These two cellular streams of migrating interneurons were completely absent in the double-mutant embryos (Fig. 1A′). Upon comparison of the YFP-stained sections from the double mutant with equivalent sections from the conditional Rac1 mutant (Fig. 1 of (Vidaki et al. 2012) and data not shown) at subsequent stages, we observed that the double-mutant cells entered the dorsal telencephalon ∼1 day later (E14.5, Fig. 1A′) than the single Rac1 mutant YFP+ cells (Fig. 1 of Vidaki et al. 2012). Analysis with a postmitotic marker of MGE-derived GABAergic interneurons, Lhx6, and a subtype specific marker, Sst verified the severely reduced number of migrating interneurons at E14.5 in the dorsal telencephalon of the double mutants (Fig. 1B,B′;C,C′). Later in embryogenesis (E16.5), in the double mutants, only a few YFP+, Lhx6+, or Sst+ cells were found inside the cortex but not extending as dorsally as in the control mice (Fig. 1D,E,F,D′,E′,F′). In addition, a significant accumulation of these cells was observed in the ventral telencephalon of double-mutant embryos and not in the control ones (asterisk in Fig. 1D′,E′,F′).Figure 1.

Bottom Line: We show that in the absence of both Rac proteins, the embryonic migration of medial ganglionic eminence-derived interneurons is further impaired.In addition, Rac1/Rac3-deficient interneurons show gross cytoskeletal defects in vitro, with the length of their leading processes significantly reduced and a clear multipolar morphology.We propose that in the absence of Rac1/Rac3, cortical interneurons fail to migrate tangentially towards the pallium due to defects in actin and microtubule cytoskeletal dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece.

No MeSH data available.


Related in: MedlinePlus